This invention relates to a control for an electrophotographic copying machine, and in particular a countdown control mechanism.
Electrophotocopy machines have gone through a number of evolutions since their first appearance. Presently, one of the more popular types of machines is generally denominated as a low volume, moderately priced, convenience-type copier. Such machines are characterized by their relatively small appearance and their ease of operation. Characteristically, they include a minimum number of controls, require little or no operator training, and have an overall simplicity of construction and operation, at least as compared to their predecessors.
Copy machines as well as many other types of repetitive cyclically operable machines are controlled by counter or countdown devices. Such devices operate the machine to make either one or multiple copies of a given document. Accordingly, it would be desirable to have a countdown device which is compatible in its simplicity and operation with the present day convenience-type copier.
There are numerous mechanical, electrical, and electromechanical devices which have been designed to control the cyclical operation of copy machines. One typical mechanical device is a pawl and ratchet arrangement whereby the pawl is periodically operated, once for each copy, in order to step down the ratchet that has been pre-set to a position corresponding to a predetermined number of copies. Examples of such relatively simple pawl and ratchet type countdown devices can be found in U.S. Pat. Nos. 3,600,085; 3,634,637; 3,756,711; 4,027,965 and 3,834,814. Other devices make use of multiple pawls or ratchets or both in order to provide a countdown mechanism, as exemplified in U.S. Pat. Nos. 3,863,052 and U.S. Pat. No. 29,274 Re. Still other pawl and ratchet type devices have optional settings which will enable an operator to continuously make a predetermined number of copies of different documents without the necessity of resetting the counter mechanism after each set of copies is made. Still other mechanical countdown devices use a slider type of mechanism with a linear scale for showing the number of copies demanding to be made. See, for example, U.S. Pat. Nos. 3,900,256 and 3,916,167.
In addition to the foregoing mechanical devices, there are a number of electrical and combined electro-mechanical countdown mechanisms. For examples of the latter, see U.S. Pat. Nos. 3,445,160, 3,482,912, 3,503,677 and 3,758,755.
Nevertheless, despite the many combinations and variations, of countdown devices shown by the prior art, there remains a need for a simple, effective countdown mechanism that is compatible in cost, construction, and operation with the now popular convenience-type copiers.
In the art of timekeeping one of the best known mechanisms to measure time is an escapement, comprising the combination of an escape wheel and an anchor. In pendulum time pieces, a weight is attached to the spindle of a toothed, escape wheel thus causing the wheel to rotate. That rotation, however, is arrested by the anchor which is linked to the pendulum. Under the control of the pendulum, the anchor periodically engages and releases the toothed wheel. Each time the pendulum reaches its maximum amplitude one of the projections (pallets) of the anchor releases a tooth of the escape wheel, allowing the wheel to rotate a corresponding amount. Its rotation therefore is formed in a series of incremental movements that are controlled by the anchor and pendulum. It is that rotation that is transmitted to the hands of the clock through a train of gear wheels. In other time pieces, such as watches, the controlling action of the pendulum is performed by a device called a balance wheel. Attached to the spindle of the balance wheel is a spiral spring named the balance spring or hair spring, which controls the oscillations of the balance. The pallets of the anchor are attached to the balance through a linkage such that with each oscillation of the lever the pallets release an escape wheel allowing it to rotate a distance corresponding to each tooth. The driving force of the escape keywheel is supplied by the wound, main spring of the watch.